Explosion-proof lamp



Sept 14, 1948- J. R. BELL ErAL 2,449,362

ExPposIoN-Pnor' LAMP Filed March 25, 1947 Inventors Patented Sept. 14, 1948 EXPLO SION-PROOF LAMP James R. Bell, La Grange, Ill., L. David Stacy, Burkburnett, Tex., and Irvin E. Dischinger, Jr., Berwyn, Ill., asslgnors to General Motors Corporation, Detroit, Mich., a corporation of Dela- Ware Application March 25, 1947, Serial No. 737,122

3 Claims. (Cl. 24U-11.2)

The present invention relates to lamps and more particularly to lamps of the explosion proof type.

The principal object of the present invention is to provide a portable explosion proof lamp housing including a lens, electric lamp, and means to prevent illumination of the lamp unless there is pressure ilow through the housing in order to properly cool the parts and pressure flow out of openings in the housing adjacent the exterior of the lens to reduce contamination of the exterior of the lens by particles in the surrounding atmos phere.

Figure 1 ofthe -drawing is a longitudinal cross sectional elevation of the lamp structure.

Figures 2 and 3 are views taken on lines 2--2 and 3--3 of Figure 1, respectivelyl with parts broken away and in section.

As best shown in Figure 1 the lamp housingl comprises two symmetrical pistol grip portions I each having an internal semicircular groove 3 in which a circular gasket 5 and the exterior circular flanged inner end portion 1 of a housing member 9 in the form of a frustrum of a cone is clamped by means of machine screws, not shown, and clamping bolts and nuts I I, shown in Figure 3, extending through openings in the pistol grip portions l. An annular lens support I3 having an externally flanged outer end portion I5 is snugly secured in the outer end of the housing 9 by machine screws I1 and to the inner face of the externally flanged inner end portion 2| of the support I3 a gasket 23 and a. lens 25 is clamped by a split retaining ring 21 of semicircular section having a clamping means 29 shown between the ends of the ring 21 to provide this clamping force. A plurality of circumferentially spaced pressure outlet openings 3| are provided in the lens support member I3 between the flanged end portions I5-2I as shown in Figures 1 and 2. The axes of these openings extend in the direction of the arrows shown in Figure 1 and intersect the axis of the annular lens support I3 at a point exterior to the lens to displace any particles in the atmosphere outside the lens surface away from this surface to reduce contamination of this surface.

An incandescent electric flood lamp 33 is supported in an insulated electrical socket member 35 secured by nuts 31 to one pistol grip member I in coaxial relation to the lens 25. The socket member 35 is provided with openings 39-40, as best illustrated in Figures 1 and 3, for passage of iluld pressure from the interior of the pistol grip members I to the interior of the housing 9 and outwardly through the outlet openings 3| in the lens supporting member I3 for the purpose described.

Pressure iroma suitable source, such as an outlet valve, not shown, on an operators helmet is applied through a flexible hose 4I shown connected at oneend by threaded connections 43 to the inlet of a pressure flow switch 45 in the outer end of the pistol grip members I. The flow switch 45 is a, conventional member having normally opened electrical switch contacts and a member, not shown, responsive to flow of pressure through the switch and outwardly through an outlet opening 41 to cause closure ci the switch contacts. A rubber covered three conductor cable 49 is also clamped between facing semicircular grooved portions in the end of the pistol grip members I. One cable conductor 5I is grounded in one pistol grip member I and the outer end is connected to ground. A second cable conductor 53 is connected to one terminal of the lamp socket member 35 and the remaining cable conductor 55 is connected to one terminal and contact of the pressure ilow switch 45. A finger operated trigger switch 51 of conventional type and having normally open contacts, not shown, which are closed upon depression of the trigger member 59 is secured snugly between the pistol grip members and the separate contacts and terminals thereon are shown connected by conductors ISI- 63 in series between the other terminal of the lamp 33 and other terminal of the ilow switch 45.

It will be evident that with the outer ends of the cable conductors 53-55 connected across an electrical source and the pressure flow switch 45, trigger switch 51 and lamp 33 connected in series relation therebetween by conductors Eil- 63 the lamp circuit can only be completed to cause illumination of the lamp by closure of the pressure ilow switch at a proper rate of pressure flow which causes circulation of fluid pressure through the interior of the pistol grip members I, openings 39--40 in the socket, around the lamp 35 in the housing 9 and outwardly through the outlet openings 3| in the lens support member to prevent contamination of the outer face lens. Fluid flow in the lamp` housing at greater pressure than the surrounding atmosphere tends to prevent entrance of atmosphere into the lamp housing and if the switches 45-59 are non-arcing type in which the contacts are sealed in a tube filled with mercury which is tipped to connect the contacts upon pressure iiow and by the trigger there is little danger of causing an explosion by use of this lamp structure even if the lamp bulb breaks. The parts of the lamp are cooled to a safe temperature in the surrounding atmosphere and long life of the lamp bulb is obtained and infrequent cleaning of the lens is necessary. By the use of light metal parts in the lamp housing and attaching the pressure hose to the operators helmet the operator may easily enter and leave srnall openings and work in confined spaces with adequate `illumination without danger ofc electric shock or explosion.

We claim:

1. A portable light source comprising an vincandescent electric lamp, a lamp housing includ-4 ing a lens adjacent said lamp, pressure outlet openings for directing pressurel flow. outwardly away from said lens, a pressureinlet connection adapted to be connected toa source of fluid'pressure, an electric switch adapted to be closed by ilow of pressure therethrough and connected to said pressure inlet connection and a Imanually operable electric lamp switch operable to a closed position from outside ysaid housing, and a power cable extending through an opening in said housing for connecting said lampand switches in series with an electrical power'source.

y2. A 'portable light source comprising an incandescent electric'ood 1arnp,a lamp housing 'includinga sealed lens adjacent said lamp, pres-4 sure outlet openings adjacent the periphery of f`said lens fordirecting pressure flow outwardly of Usaid housing to a point on the axis of said lens,

apistol'grip'housing portion including a pressureinlet'connection'adapted to be connected to a source of fluid pressure, a-n electric switch connected to said pressure source and adapted to be closed fbyiiow of'pressure through said -housing, a trigger'closed electric'switch and an electric cable extending snugly through an opening in said pistol grip housing portion for connecting said lamp and switches in series with an electrical source.

3. A portable light source comprising an incandescent electric flood lamp, a lightweight lamp housing havingv end openings, a lens sealed ...in ,one opening,l said housing having circumferentially spaced pressure outlet openings adjaicent said lens for directing fluid pressure flow outwardly of said housing toward a point on the `axis'of said lens, a hollow pistol grip clamped in .c luid tight relation with said other lamp housing openingand?, including a trigger closed electric switchandasecond electric switch adapted to be v-REFERENCES `CITED 'The'iollowing references are -of vrecord in the 'file cf-this patent:

f STATES PATENTS Number Name Date 446,142 Martin Feb. 10, 1891 721,646 Kirby Feb. 24, 193

1,595,870 "Robinson Aug. 10, 1926 1,823,535 fF-rutkowet al Sept. 15, 1931 

